Related
Is there a nice way I can convert a Scala case class instance, e.g.
case class MyClass(param1: String, param2: String)
val x = MyClass("hello", "world")
into a mapping of some kind, e.g.
getCCParams(x) returns "param1" -> "hello", "param2" -> "world"
Which works for any case class, not just predefined ones. I've found you can pull the case class name out by writing a method that interrogates the underlying Product class, e.g.
def getCCName(caseobj: Product) = caseobj.productPrefix
getCCName(x) returns "MyClass"
So I'm looking for a similar solution but for the case class fields. I'd imagine a solution might have to use Java reflection, but I'd hate to write something that might break in a future release of Scala if the underlying implementation of case classes changes.
Currently I'm working on a Scala server and defining the protocol and all its messages and exceptions using case classes, as they are such a beautiful, concise construct for this. But I then need to translate them into a Java map to send over the messaging layer for any client implementation to use. My current implementation just defines a translation for each case class separately, but it would be nice to find a generalised solution.
This should work:
def getCCParams(cc: AnyRef) =
cc.getClass.getDeclaredFields.foldLeft(Map.empty[String, Any]) { (a, f) =>
f.setAccessible(true)
a + (f.getName -> f.get(cc))
}
Because case classes extend Product one can simply use .productIterator to get field values:
def getCCParams(cc: Product) = cc.getClass.getDeclaredFields.map( _.getName ) // all field names
.zip( cc.productIterator.to ).toMap // zipped with all values
Or alternatively:
def getCCParams(cc: Product) = {
val values = cc.productIterator
cc.getClass.getDeclaredFields.map( _.getName -> values.next ).toMap
}
One advantage of Product is that you don't need to call setAccessible on the field to read its value. Another is that productIterator doesn't use reflection.
Note that this example works with simple case classes that don't extend other classes and don't declare fields outside the constructor.
Starting Scala 2.13, case classes (as implementations of Product) are provided with a productElementNames method which returns an iterator over their field's names.
By zipping field names with field values obtained with productIterator we can generically obtain the associated Map:
// case class MyClass(param1: String, param2: String)
// val x = MyClass("hello", "world")
(x.productElementNames zip x.productIterator).toMap
// Map[String,Any] = Map("param1" -> "hello", "param2" -> "world")
If anybody looks for a recursive version, here is the modification of #Andrejs's solution:
def getCCParams(cc: Product): Map[String, Any] = {
val values = cc.productIterator
cc.getClass.getDeclaredFields.map {
_.getName -> (values.next() match {
case p: Product if p.productArity > 0 => getCCParams(p)
case x => x
})
}.toMap
}
It also expands the nested case-classes into maps at any level of nesting.
Here's a simple variation if you don't care about making it a generic function:
case class Person(name:String, age:Int)
def personToMap(person: Person): Map[String, Any] = {
val fieldNames = person.getClass.getDeclaredFields.map(_.getName)
val vals = Person.unapply(person).get.productIterator.toSeq
fieldNames.zip(vals).toMap
}
scala> println(personToMap(Person("Tom", 50)))
res02: scala.collection.immutable.Map[String,Any] = Map(name -> Tom, age -> 50)
If you happen to be using Json4s, you could do the following:
import org.json4s.{Extraction, _}
case class MyClass(param1: String, param2: String)
val x = MyClass("hello", "world")
Extraction.decompose(x)(DefaultFormats).values.asInstanceOf[Map[String,String]]
Solution with ProductCompletion from interpreter package:
import tools.nsc.interpreter.ProductCompletion
def getCCParams(cc: Product) = {
val pc = new ProductCompletion(cc)
pc.caseNames.zip(pc.caseFields).toMap
}
You could use shapeless.
Let
case class X(a: Boolean, b: String,c:Int)
case class Y(a: String, b: String)
Define a LabelledGeneric representation
import shapeless._
import shapeless.ops.product._
import shapeless.syntax.std.product._
object X {
implicit val lgenX = LabelledGeneric[X]
}
object Y {
implicit val lgenY = LabelledGeneric[Y]
}
Define two typeclasses to provide the toMap methods
object ToMapImplicits {
implicit class ToMapOps[A <: Product](val a: A)
extends AnyVal {
def mkMapAny(implicit toMap: ToMap.Aux[A, Symbol, Any]): Map[String, Any] =
a.toMap[Symbol, Any]
.map { case (k: Symbol, v) => k.name -> v }
}
implicit class ToMapOps2[A <: Product](val a: A)
extends AnyVal {
def mkMapString(implicit toMap: ToMap.Aux[A, Symbol, Any]): Map[String, String] =
a.toMap[Symbol, Any]
.map { case (k: Symbol, v) => k.name -> v.toString }
}
}
Then you can use it like this.
object Run extends App {
import ToMapImplicits._
val x: X = X(true, "bike",26)
val y: Y = Y("first", "second")
val anyMapX: Map[String, Any] = x.mkMapAny
val anyMapY: Map[String, Any] = y.mkMapAny
println("anyMapX = " + anyMapX)
println("anyMapY = " + anyMapY)
val stringMapX: Map[String, String] = x.mkMapString
val stringMapY: Map[String, String] = y.mkMapString
println("anyMapX = " + anyMapX)
println("anyMapY = " + anyMapY)
}
which prints
anyMapX = Map(c -> 26, b -> bike, a -> true)
anyMapY = Map(b -> second, a -> first)
stringMapX = Map(c -> 26, b -> bike, a -> true)
stringMapY = Map(b -> second, a -> first)
For nested case classes, (thus nested maps)
check another answer
I don't know about nice... but this seems to work, at least for this very very basic example. It probably needs some work but might be enough to get you started? Basically it filters out all "known" methods from a case class (or any other class :/ )
object CaseMappingTest {
case class MyCase(a: String, b: Int)
def caseClassToMap(obj: AnyRef) = {
val c = obj.getClass
val predefined = List("$tag", "productArity", "productPrefix", "hashCode",
"toString")
val casemethods = c.getMethods.toList.filter{
n =>
(n.getParameterTypes.size == 0) &&
(n.getDeclaringClass == c) &&
(! predefined.exists(_ == n.getName))
}
val values = casemethods.map(_.invoke(obj, null))
casemethods.map(_.getName).zip(values).foldLeft(Map[String, Any]())(_+_)
}
def main(args: Array[String]) {
println(caseClassToMap(MyCase("foo", 1)))
// prints: Map(a -> foo, b -> 1)
}
}
commons.mapper.Mappers.Mappers.beanToMap(caseClassBean)
Details: https://github.com/hank-whu/common4s
With the use of Java reflection, but no change of access level. Converts Product and case class to Map[String, String]:
def productToMap[T <: Product](obj: T, prefix: String): Map[String, String] = {
val clazz = obj.getClass
val fields = clazz.getDeclaredFields.map(_.getName).toSet
val methods = clazz.getDeclaredMethods.filter(method => fields.contains(method.getName))
methods.foldLeft(Map[String, String]()) { case (acc, method) =>
val value = method.invoke(obj).toString
val key = if (prefix.isEmpty) method.getName else s"${prefix}_${method.getName}"
acc + (key -> value)
}
}
Modern variation with Scala 3 might also be a bit simplified as with the following example that is similar to the answer posted by Walter Chang above.
def getCCParams(cc: AnyRef): Map[String, Any] =
cc.getClass.getDeclaredFields
.tapEach(_.setAccessible(true))
.foldLeft(Map.empty)((a, f) => a + (f.getName -> f.get(cc)))
Let's say i have 2 cases classes:
case class Money(amount: Int, currency: String)
case class Human(name: String, money: Money)
is there a nice way to "translate" a list of strings to class Human? smth like:
def superMethod[A](params: List[String]): A = ???
val params: List[Any] = List("john", 100, "dollar")
superMethod(params) // => Human("john", Money(100, "dollar"))
so essentially i know type A only in runtime
UPDATE: i found ~ what i was looking for. it seems i can do it via shapeless. example i found in github
Here is an implementation that works for generic classes A.
It relies on runtime reflection (that is, a different TypeTag can be passed to the method at runtime). The following obvious conditions must be fulfilled in order to use this method:
A must be on the class path, or otherwise be loadable by the used class loader
TypeTag must be available for A at the call site.
The actual implementation is in the Deserializer object. Then comes a little demo.
The deserializer:
import scala.reflect.runtime.universe.{TypeTag, Type}
object Deserializer {
/** Extracts an instance of type `A` from the
* flattened `Any` constructor arguments, and returns
* the constructed instance together with the remaining
* unused arguments.
*/
private def deserializeRecHelper(
flattened: List[Any],
tpe: Type
): (Any, List[Any]) = {
import scala.reflect.runtime.{universe => ru}
// println("Trying to deserialize " + tpe + " from " + flattened)
// println("Constructor alternatives: ")
// val constructorAlternatives = tpe.
// member(ru.termNames.CONSTRUCTOR).
// asTerm.
// alternatives.foreach(println)
val consSymb = tpe.
member(ru.termNames.CONSTRUCTOR).
asTerm.
alternatives(0).
asMethod
val argsTypes: List[Type] = consSymb.paramLists(0).map(_.typeSignature)
if (tpe =:= ru.typeOf[String] || argsTypes.isEmpty) {
val h :: t = flattened
(h, t)
} else {
val args_rems: List[(Any, List[Any])] = argsTypes.scanLeft(
(("throwaway-sentinel-in-deserializeRecHelper": Any), flattened)
) {
case ((_, remFs), t) =>
deserializeRecHelper(remFs, t)
}.tail
val remaining: List[Any] = args_rems.last._2
val args: List[Any] = args_rems.unzip._1
val runtimeMirror = ru.runtimeMirror(getClass.getClassLoader)
val classMirror = runtimeMirror.reflectClass(tpe.typeSymbol.asClass)
val cons = classMirror.reflectConstructor(consSymb)
// println("Build constructor arguments array for " + tpe + " : " + args)
val obj = cons.apply(args:_*)
(obj, remaining)
}
}
def deserialize[A: TypeTag](flattened: List[Any]): A = {
val (a, rem) = deserializeRecHelper(
flattened,
(implicitly: TypeTag[A]).tpe
)
require(
rem.isEmpty,
"Superfluous arguments remained after deserialization: " + rem
)
a.asInstanceOf[A]
}
}
Demo:
case class Person(id: String, money: Money, pet: Pet, lifeMotto: String)
case class Money(num: Int, currency: String)
case class Pet(color: String, species: Species)
case class Species(description: String, name: String)
object Example {
def main(args: Array[String]): Unit = {
val data = List("Bob", 42, "USD", "pink", "invisible", "unicorn", "what's going on ey?")
val p = Deserializer.deserialize[Person](data)
println(p)
}
}
Output:
Person(Bob,Money(42,USD),Pet(pink,Species(invisible,unicorn)),what's going on ey?)
Discussion
This implementation is not restricted to case classes, but it requires each "Tree-node-like" class to have exactly one constructor that accepts either
primitive types (Int, Float), or
strings, or
other "Tree-node-like" classes.
Note that the task is somewhat ill-posed: what does it mean to say that all constructor arguments are flattened in a single list? Given the class Person(name: String, age: Int), will the List[Any] contain every single byte of the name as a separate entry? Probably not. Therefore, strings are handled by the deserializer in a special way, and all other collection-like entities are not supported for the same reasons (unclear where to stop parsing, because size of the collection is not known).
In case A is not a generic type, but effectively Human, you can use a companion object to the case class Human:
object Human {
def fromList(list: List[String]): Human = list match {
case List(name, amount, currency) => Human(name, Money(amount.toInt, currency))
case _ => handle corner case
}
}
Which you can call:
Human.fromList(List("john", "100", "dollar"))
To make it safe, don't forget to handle the case of lists whose size wouldn't be 3; and of lists whose 2nd element can't be cast to an Int:
import scala.util.Try
object Human {
def fromList(list: List[String]): Option[Human] = list match {
case List(name, amount, currency) =>
Try(Human(name, Money(amount.toInt, currency))).toOption
case _ => None
}
}
Edit: Based on your last comment, you might find this usefull:
case class Money(amount: Int, currency: String)
case class Human(name: String, money: Money)
case class SomethingElse(whatever: Double)
object Mapper {
def superMethod(list: List[String]): Option[Any] =
list match {
case List(name, amount, currency) =>
Try(Human(name, Money(amount.toInt, currency))).toOption
case List(whatever) => Try(SomethingElse(whatever.toDouble)).toOption
case _ => None
}
}
println(Mapper.superMethod(List("john", 100, "dollar")))
> Some(Human(john,Money(100,dollar)))
println(Mapper.superMethod(List(17d)))
> Some(SomethingElse(17.0))
or alternatively:
object Mapper {
def superMethod[A](list: List[String]): Option[A] =
(list match {
case List(name, amount, currency) =>
Try(Human(name, Money(amount, currency))).toOption
case List(whatever) =>
Try(SomethingElse(whatever.toDouble)).toOption
case _ => None
}).map(_.asInstanceOf[A])
}
println(Mapper.superMethod[Human](List("john", "100", "dollar")))
> Some(Human(john,Money(100,dollar)))
println(Mapper.superMethod[SomethingElse](List("17.2")))
> Some(SomethingElse(17.0))
I have a generic map with values, some of which can be in turn lists of values.
I'm trying to process a given key and convert the results to the type expected by an outside caller, like this:
// A map with some values being other collections.
val map: Map[String, Any] = Map("foo" -> 1, "bar" -> Seq('a', 'b'. 'a'))
// A generic method with a "specialization" for collections (pseudocode)
def cast[T](key: String) = map.get(key).map(_.asInstanceOf[T])
def cast[C <: Iterable[T]](key: String) = map.get(key).map(list => list.to[C].map(_.asIntanceOf[T]))
// Expected usage
cast[Int]("foo") // Should return 1:Int
cast[Set[Char]]("bar") // Should return Set[Char]('a', 'b')
This is to show what I would like to do, but it does not work. The compiler error complains (correctly, about 2 possible matches). I've also tried to make this a single function with some sort of pattern match on the type to no avail.
I've been reading on #specialized, TypeTag, CanBuildFrom and other scala functionality, but I failed to find a simple way to put it all together. Separate examples I've found address different pieces and some ugly workarounds, but nothing that would simply allow an external user to call cast and get an exception is the cast was invalid. Some stuff is also old, I'm using Scala 2.10.5.
This appears to work but it has a some problems.
def cast[T](m: Map[String, Any], k: String):T = m(k) match {
case x: T => x
}
With the right input you get the correct output.
scala> cast[Int](map,"foo")
res18: Int = 1
scala> cast[Set[Char]](map,"bar")
res19: Set[Char] = Set(a, b)
But it throws if the type is wrong for the key or if the map has no such key (of course).
You can do this via implicit parameters:
val map: Map[String, Any] = Map("foo" -> 1, "bar" -> Set('a', 'b'))
abstract class Casts[B] {def cast(a: Any): B}
implicit val doubleCast = new Casts[Double] {
override def cast(a: Any): Double = a match {
case x: Int => x.toDouble
}
}
implicit val intCast = new Casts[Int] {
override def cast(a: Any): Int = a match {
case x: Int => x
case x: Double => x.toInt
}
}
implicit val seqCharCast = new Casts[Seq[Char]] {
override def cast(a: Any): Seq[Char] = a match {
case x: Set[Char] => x.toSeq
case x: Seq[Char] => x
}
}
def cast[T](key: String)(implicit p:Casts[T]) = p.cast(map(key))
println(cast[Double]("foo")) // <- 1.0
println(cast[Int]("foo")) // <- 1
println(cast[Seq[Char]]("bar")) // <- ArrayBuffer(a, b) which is Seq(a, b)
But you still need to iterate over all type-to-type options, which is reasonable as Set('a', 'b').asInstanceOf[Seq[Char]] throws, and you cannot use a universal cast, so you need to handle such cases differently.
Still it sounds like an overkill, and you may need to review your approach from global perspective
What I need is a class X I can construct with a Map that takes Strings into either other Strings or Maps that take Strings into Strings, and then an arbitrary number of other instances of X. With my limited grasp of Scala, I know I can do this:
class Person (stringParms : Map[String, String],
mapParms : Map[String, Map[String, String]],
children : List[X]) {
}
but that doesn't look very Scala-ish ("Scalish"? "Scalerific"? "Scalogical"?) I'd like to be able to do is the following:
Person bob = Person("name" -> "Bob", "pets" -> ("cat" -> "Mittens", "dog" -> "Spot"), "status" -> "asleep",
firstChild, secondChild)
I know I can get rid of the "new" by using the companion object and I'm sure I can look Scala varargs. What I'd like to know is:
How I can use -> (or some similarly plausible operator) to construct elements to be made into a Map in the construction?
How I can define a single map so either it can do an Option-like switch between two very disparate types or becomes a recursive tree, where each (named) node points to either a leaf in the form of a String or another node like itself?
The recursive version really appeals to me because, although it doesn't address a problem I actually have today, it maps neatly into a subset of JSON containing only objects and strings (no numbers or arrays).
Any help, as always, greatly appreciated.
-> is just a syntactic sugar to make a pair (A, B), so you can use it too. Map object takes a vararg of pairs:
def apply [A, B] (elems: (A, B)*) : Map[A, B]
You should first check out The Architecture of Scala Collections if you're interested in mimicking the collections library.
Having said that, I don't think the signature you proposed for Person looks like Map, because it expects variable argument, yet children are not continuous with the other (String, A) theme. If you say "child1" -> Alice, and internally store Alice seperately, you could define:
def apply(elems: (String, Any)*): Person
in the companion object. If Any is too loose, you could define PersonElem trait,
def apply(elems: (String, PersonElem)*): Person
and implicit conversion between String, Map[String, String], Person, etc to PersonElem.
This gets you almost there. There is still a Map I don't get easily rid of.
The basic approach is to have a somewhat artificial parameter types, which inherit from a common type. This way the apply method just takes a single vararg.
Using implicit conversion method I get rid of the ugly constructors for the parameter types
case class Child
case class Person(stringParms: Map[String, String],
mapParms: Map[String, Map[String, String]],
children: List[Child]) { }
sealed abstract class PersonParameter
case class MapParameter(tupel: (String, Map[String, String])) extends PersonParameter
case class StringParameter(tupel: (String, String)) extends PersonParameter
case class ChildParameter(child: Child) extends PersonParameter
object Person {
def apply(params: PersonParameter*): Person = {
var stringParms = Map[String, String]()
var mapParms = Map[String, Map[String, String]]()
var children = List[Child]()
for (p ← params) {
p match {
case StringParameter(t) ⇒ stringParms += t
case MapParameter(t) ⇒ mapParms += t
case ChildParameter(c) ⇒ children = c :: children
}
}
new Person(stringParms, mapParms, children)
}
implicit def tupel2StringParameter(t: (String, String)) = StringParameter(t)
implicit def child2ChildParameter(c: Child) = ChildParameter(c)
implicit def map2MapParameter(t: (String, Map[String, String])) = MapParameter(t)
def main(args: Array[String]) {
val firstChild = Child()
val secondChild = Child()
val bob: Person = Person("name" -> "Bob","pets" -> Map("cat" -> "Mittens", "dog" -> "Spot"),"status"
-> "asleep",
firstChild, secondChild)
println(bob)
} }
Here's one way:
sealed abstract class PersonParam
object PersonParam {
implicit def toTP(tuple: (String, String)): PersonParam = new TupleParam(tuple)
implicit def toMap(map: (String, Map[String, String])): PersonParam = new MapParam(map)
implicit def toSP(string: String): PersonParam = new StringParam(string)
}
class TupleParam(val tuple: (String, String)) extends PersonParam
class MapParam(val map: (String, Map[String, String])) extends PersonParam
class StringParam(val string: String) extends PersonParam
class Person(params: PersonParam*) {
val stringParams = Map(params collect { case parm: TupleParam => parm.tuple }: _*)
val mapParams = Map(params collect { case parm: MapParam => parm.map }: _*)
val children = params collect { case parm: StringParam => parm.string } toList
}
Usage:
scala> val bob = new Person("name" -> "Bob",
| "pets" -> Map("cat" -> "Mittens", "dog" -> "Spot"),
| "status" -> "asleep",
| "little bob", "little ann")
bob: Person = Person#5e5fada2
scala> bob.stringParams
res11: scala.collection.immutable.Map[String,String] = Map((name,Bob), (status,asleep))
scala> bob.mapParams
res12: scala.collection.immutable.Map[String,Map[String,String]] = Map((pets,Map(cat -> Mittens, dog -> Spot)))
scala> bob.children
res13: List[String] = List(little bob, little ann)
Is there a nice way I can convert a Scala case class instance, e.g.
case class MyClass(param1: String, param2: String)
val x = MyClass("hello", "world")
into a mapping of some kind, e.g.
getCCParams(x) returns "param1" -> "hello", "param2" -> "world"
Which works for any case class, not just predefined ones. I've found you can pull the case class name out by writing a method that interrogates the underlying Product class, e.g.
def getCCName(caseobj: Product) = caseobj.productPrefix
getCCName(x) returns "MyClass"
So I'm looking for a similar solution but for the case class fields. I'd imagine a solution might have to use Java reflection, but I'd hate to write something that might break in a future release of Scala if the underlying implementation of case classes changes.
Currently I'm working on a Scala server and defining the protocol and all its messages and exceptions using case classes, as they are such a beautiful, concise construct for this. But I then need to translate them into a Java map to send over the messaging layer for any client implementation to use. My current implementation just defines a translation for each case class separately, but it would be nice to find a generalised solution.
This should work:
def getCCParams(cc: AnyRef) =
cc.getClass.getDeclaredFields.foldLeft(Map.empty[String, Any]) { (a, f) =>
f.setAccessible(true)
a + (f.getName -> f.get(cc))
}
Because case classes extend Product one can simply use .productIterator to get field values:
def getCCParams(cc: Product) = cc.getClass.getDeclaredFields.map( _.getName ) // all field names
.zip( cc.productIterator.to ).toMap // zipped with all values
Or alternatively:
def getCCParams(cc: Product) = {
val values = cc.productIterator
cc.getClass.getDeclaredFields.map( _.getName -> values.next ).toMap
}
One advantage of Product is that you don't need to call setAccessible on the field to read its value. Another is that productIterator doesn't use reflection.
Note that this example works with simple case classes that don't extend other classes and don't declare fields outside the constructor.
Starting Scala 2.13, case classes (as implementations of Product) are provided with a productElementNames method which returns an iterator over their field's names.
By zipping field names with field values obtained with productIterator we can generically obtain the associated Map:
// case class MyClass(param1: String, param2: String)
// val x = MyClass("hello", "world")
(x.productElementNames zip x.productIterator).toMap
// Map[String,Any] = Map("param1" -> "hello", "param2" -> "world")
If anybody looks for a recursive version, here is the modification of #Andrejs's solution:
def getCCParams(cc: Product): Map[String, Any] = {
val values = cc.productIterator
cc.getClass.getDeclaredFields.map {
_.getName -> (values.next() match {
case p: Product if p.productArity > 0 => getCCParams(p)
case x => x
})
}.toMap
}
It also expands the nested case-classes into maps at any level of nesting.
Here's a simple variation if you don't care about making it a generic function:
case class Person(name:String, age:Int)
def personToMap(person: Person): Map[String, Any] = {
val fieldNames = person.getClass.getDeclaredFields.map(_.getName)
val vals = Person.unapply(person).get.productIterator.toSeq
fieldNames.zip(vals).toMap
}
scala> println(personToMap(Person("Tom", 50)))
res02: scala.collection.immutable.Map[String,Any] = Map(name -> Tom, age -> 50)
If you happen to be using Json4s, you could do the following:
import org.json4s.{Extraction, _}
case class MyClass(param1: String, param2: String)
val x = MyClass("hello", "world")
Extraction.decompose(x)(DefaultFormats).values.asInstanceOf[Map[String,String]]
Solution with ProductCompletion from interpreter package:
import tools.nsc.interpreter.ProductCompletion
def getCCParams(cc: Product) = {
val pc = new ProductCompletion(cc)
pc.caseNames.zip(pc.caseFields).toMap
}
You could use shapeless.
Let
case class X(a: Boolean, b: String,c:Int)
case class Y(a: String, b: String)
Define a LabelledGeneric representation
import shapeless._
import shapeless.ops.product._
import shapeless.syntax.std.product._
object X {
implicit val lgenX = LabelledGeneric[X]
}
object Y {
implicit val lgenY = LabelledGeneric[Y]
}
Define two typeclasses to provide the toMap methods
object ToMapImplicits {
implicit class ToMapOps[A <: Product](val a: A)
extends AnyVal {
def mkMapAny(implicit toMap: ToMap.Aux[A, Symbol, Any]): Map[String, Any] =
a.toMap[Symbol, Any]
.map { case (k: Symbol, v) => k.name -> v }
}
implicit class ToMapOps2[A <: Product](val a: A)
extends AnyVal {
def mkMapString(implicit toMap: ToMap.Aux[A, Symbol, Any]): Map[String, String] =
a.toMap[Symbol, Any]
.map { case (k: Symbol, v) => k.name -> v.toString }
}
}
Then you can use it like this.
object Run extends App {
import ToMapImplicits._
val x: X = X(true, "bike",26)
val y: Y = Y("first", "second")
val anyMapX: Map[String, Any] = x.mkMapAny
val anyMapY: Map[String, Any] = y.mkMapAny
println("anyMapX = " + anyMapX)
println("anyMapY = " + anyMapY)
val stringMapX: Map[String, String] = x.mkMapString
val stringMapY: Map[String, String] = y.mkMapString
println("anyMapX = " + anyMapX)
println("anyMapY = " + anyMapY)
}
which prints
anyMapX = Map(c -> 26, b -> bike, a -> true)
anyMapY = Map(b -> second, a -> first)
stringMapX = Map(c -> 26, b -> bike, a -> true)
stringMapY = Map(b -> second, a -> first)
For nested case classes, (thus nested maps)
check another answer
I don't know about nice... but this seems to work, at least for this very very basic example. It probably needs some work but might be enough to get you started? Basically it filters out all "known" methods from a case class (or any other class :/ )
object CaseMappingTest {
case class MyCase(a: String, b: Int)
def caseClassToMap(obj: AnyRef) = {
val c = obj.getClass
val predefined = List("$tag", "productArity", "productPrefix", "hashCode",
"toString")
val casemethods = c.getMethods.toList.filter{
n =>
(n.getParameterTypes.size == 0) &&
(n.getDeclaringClass == c) &&
(! predefined.exists(_ == n.getName))
}
val values = casemethods.map(_.invoke(obj, null))
casemethods.map(_.getName).zip(values).foldLeft(Map[String, Any]())(_+_)
}
def main(args: Array[String]) {
println(caseClassToMap(MyCase("foo", 1)))
// prints: Map(a -> foo, b -> 1)
}
}
commons.mapper.Mappers.Mappers.beanToMap(caseClassBean)
Details: https://github.com/hank-whu/common4s
With the use of Java reflection, but no change of access level. Converts Product and case class to Map[String, String]:
def productToMap[T <: Product](obj: T, prefix: String): Map[String, String] = {
val clazz = obj.getClass
val fields = clazz.getDeclaredFields.map(_.getName).toSet
val methods = clazz.getDeclaredMethods.filter(method => fields.contains(method.getName))
methods.foldLeft(Map[String, String]()) { case (acc, method) =>
val value = method.invoke(obj).toString
val key = if (prefix.isEmpty) method.getName else s"${prefix}_${method.getName}"
acc + (key -> value)
}
}
Modern variation with Scala 3 might also be a bit simplified as with the following example that is similar to the answer posted by Walter Chang above.
def getCCParams(cc: AnyRef): Map[String, Any] =
cc.getClass.getDeclaredFields
.tapEach(_.setAccessible(true))
.foldLeft(Map.empty)((a, f) => a + (f.getName -> f.get(cc)))